There are mobile phones including a wireless local area network (WLAN) interface for connection with a WLAN. Such mobile phones include a function for packet communications via a WLAN in addition to a basic function for circuit-switched communications.
Generally, mobile phones use a WLAN for voice communications and data communications. Voice communications are performed using an IP phone technology where packetized voice information is transmitted and received via the voice over Internet protocol (VoIP). Voice communications via a WLAN, for example, make it possible to use mobile phones as internal phones in a company. An example of data communications is Web browsing on the Internet. A mobile phone including a full browser enables browsing Web sites designed for personal computers.
For voice communications, to be able to respond to an incoming call at any time, it is preferable to keep a mobile phone ready for communications with an access point (AP), a radio station for the WLAN. When the mobile phone moves away from the AP or the signal strength of a beacon from the AP becomes low for some reason, the mobile phone performs a scanning process to search for another AP (see, for example, Japanese Laid-Open Patent Publication No. 2005-175932). Here, since it is no use performing a scanning process in an out-of-service area, a method has been proposed to reduce the number of times the scanning process is performed. In the proposed method, the scan interval is gradually increased to reduce wasteful power consumption caused by unnecessary scanning (see, for example, Japanese Laid-Open Patent Publication No. 2006-13549).
Meanwhile, data communications such as Web browsing are generally started by user operations. Therefore, if a mobile phone does not include a function for voice communications via the WLAN, the WLAN interface of the mobile phone may be turned off when data communications are completed or after a predetermined period of time from the end of data communications to reduce the power consumption.